JPH05142603A - Nonlinear optical material - Google Patents

Abstract

PURPOSE:To obtain a low mol.wt. org. material having x<(3)> equal to or larger than that of pi conjugate polymers by using such an org. material having substitution of alkyl amino groups for both ends of the molecule and two or more specified conjugate bonds. CONSTITUTION:This material has substitution of alkyl amino groups for both ends of the molecule and two or more -CH=CH-CO as conjugate bonds. The material has high x<(3)> which exceeds 10<-10> esu, and is a pi-conjugate compd. having a symmetric structure with substitution of electron donating groups (donors) at both ends of the molecule. By using this material to constitute a principal-chain or side-chain polymer material, for example, with even 50mol% introduction rate, a material having high light transmitting property and formability can be produced since the low mol.wt. material can be easily coupled with a polymer material having excellent light transmitting property and formability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical nonlinear main chain type polymer material applicable to an optical gate device, an optical bistable device and the like which are basic devices of optical computing.

[0002]

2. Description of the Related Art When light is incident on a substance, the electric polarization P of the substance induced by a photoelectric field E can be expressed by the following general formula (Equation 1).

[0003]

[Equation 1] P = χ ⁽¹⁾ E + χ ⁽²⁾ EE + χ ⁽³⁾ EEE + ...

At this time, χ ⁽ⁱ⁾ (i ≧ 2) is called an i-th order nonlinear susceptibility. Second harmonic generation (SH
G) and the third harmonic generation (THG) according to the third term are well known as the wavelength conversion effect. The third term is also important as giving a change in the optical constant according to the light intensity, for example, a nonlinear refractive index effect or a nonlinear absorption effect. Among them, the nonlinear refractive index effect is such that the refractive index n of a substance changes in proportion to the incident light intensity, and is described by the following formula (Equation 2).

[0005]

## EQU2 ## n = n ₀ + n ₂ I

N ₀ is the refractive index at weak light intensity, and I is the incident light intensity. n ₂ is a nonlinear refractive index, and the relationship of the following equation (Equation 3) holds between n ₂ and the third-order nonlinear susceptibility: χ ⁽³⁾ (C is the speed of light). Both n ₂ and χ ⁽³⁾ are used as an index indicating the magnitude of the nonlinear effect.

[0007]

N ₂ = (16π ² / Cn ₀ ² ) χ ⁽³⁾

When a material exhibiting this effect is combined with another optical element such as an optical resonator, a polarizer or a reflecting mirror, an optical non-linear element such as an optical bistable element, an optical gate element or a phase conjugate wave generator is realized. Is possible. These optical non-linear elements are highly expected as key devices for future optical computing / optical switching technologies. [For general information on optical non-linear elements, refer to the Conference on Lectures of the IEEE International Conference Communications (Conf.Lec. IEEE). Int. Conf. Com
mun.) 1990 edition, page 1152 (1990)]. Among the materials that exhibit the third-order nonlinear optical effect,
Recently, an organic material having a π-electron conjugation capable of high-speed response has been particularly attracting attention. Specific examples thereof include π-conjugated polymers such as polydiacetylene, polyacetylene, and polyarylene vinylene. The nonlinear optical effect of organic materials with π-electron conjugation is purely due to electronic polarization, not due to lattice interaction like semiconductors and dielectrics.
The response speed that can follow the intensity change of the optical signal is 10 ^-14 sec
And is extremely fast. Furthermore, if poly [2,4-hexadiyne-1,6- (p-toluenesulfonate)] (abbreviation: PTS), which is one type of polydiacetylene, is taken as an example and described, the usable input wavelength range is 0. .65 μm
The nonlinear refractive index (n ₂ ) is 2 × 10 ⁻¹² (W / cm ² ) ⁻¹ over a wide range from the vicinity to 2.0 μm or more, which is two orders of magnitude higher than that of the CS ₂ liquid. Therefore, organic materials with π-electron conjugation are considered to be the most promising material system among many candidate materials for the realization of optical nonlinear devices [For the optical nonlinear characteristics of PTS, see Physical Review Letters (Physical Review Letters). Physical Review Letters) 3rd
6, Vol. 956 (1976)]. However, most of π-conjugated polymers with large χ ⁽³⁾ are insoluble and infusible and poor in workability. Even if it can be formed into a film, it has low optical transparency due to its rigidity and crystallinity, lacks formability into a desired waveguide structure, and it is extremely difficult to use it as an element as it is. It was

Therefore, a high χ ⁽³⁾ organic low-molecular material is incorporated into the side chain or the main chain of a polymer material having a high processability, and a material having a high χ ⁽³⁾ and a high processability is obtained. Has recently been proposed, and materials suitable for this have also been reported [Reference: Kurihara et al .: Journal of Applied.
Physics (Jounal of Appl. Phys.), Vol. 70, p. 17 (1991)]. However, such high χ
⁽³⁾ There are not so many kinds of organic low molecular weight materials, and there are only several kinds of materials in addition to the examples given in the above literature.

[0010]

Therefore, in order to solve the above problems, the present invention proposes a low molecular weight organic material having χ ⁽³⁾ comparable to or exceeding a π-conjugated polymer, and The purpose of the present invention is to provide a material having high χ ⁽³⁾ by incorporating the material into the side chain or main chain of a polymer material having high processability and yet having high processability.

[0011]

The present invention will be described in brief. The present invention relates to a third-order nonlinear optical material, wherein both ends of the molecule are substituted with alkylamino groups, and as a π-conjugated bond, It is characterized by having two or more CH = CH-CO-.

[0012] High chi ⁽³⁾ substances that are proposed in the present invention, both ends of the molecule are π-conjugated compounds of the symmetrical structure substituted with an electron donating group (donor), the chi ⁽³⁾ is well 10 ^-10 es
exceeds u. Also, by using a main chain type or side chain type polymer material, even if the introduction rate is 50 mol%, it can be easily bonded to a polymer material excellent in transparency and processability, so that the light transmittance It is possible to create easily workable materials.

The χ ⁽³⁾ expressing substance used in the present invention is a π-conjugated bond C having a carbonyl group (CO group) having a relatively strong acceptor property as a π-conjugated bond in a π-electron conjugated chain.
= C-CO, and since it has an alkylamino group that is a donor substituent at both ends of the π-electron conjugated chain, a π-electron that simply bonds only with a π-conjugated bond such as C = C Strong interaction with light in an excited state can be expected as compared with a material having a conjugated chain, and a much larger third-order nonlinear susceptibility can be obtained with the same molecular chain length. It is necessary that C = C-CO as a π-conjugated bond have at least two or more in the molecule. Ie 1
In the case of individual pieces, a symmetric structure cannot be obtained, and a sufficient π-conjugation length sufficient to exhibit a large optical nonlinearity cannot be obtained.

Further, the symmetric-substitution high χ ⁽³⁾ substance of the present invention can have a highly reactive substituent such as a hydroxyl group in the donors at both ends of the molecule in advance. The main chain type polymer material having a polyurethane structure or a polyester structure can be easily obtained by the above-mentioned polymerization addition reaction or polycondensation reaction with dicarboxylic acid.
Further, it is possible to react with methacrylic acid, and it is easy to form a side chain type polymer material in which the symmetrically substituted high χ ⁽³⁾ substance of the present invention is hung on the side chain.

In the polymer material of the present invention, the main chain type polymer connecting the high χ ⁽³⁾ materials is described only with polyurethane or polyester, and the polymer that hangs the high χ ⁽³⁾ material on the side chain is described. In the above description, the main chain polymer in (1) is only polymethacrylate, but the material of the present invention is not limited to this, and similar effects can be expected with other polymer materials.

[0016]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 To 200 cc of a tetrahydrofuran (THF) solution prepared by dissolving 0.2 mol of 4-diethylaminobenzaldehyde in 0.1 mol of p-diacetylbenzene was added a 10% sodium hydroxide aqueous solution, and the mixture was heated under reflux for one day. .. The precipitated crystals were recrystallized with a THF solution to obtain a compound A represented by the following formula (Formula 1), which is one of the materials of the present invention. (Melting point 160 ° C)

[0018]

[Chemical 1]

Next, the χ ⁽³⁾ value of the thin film of this material was measured by the third harmonic (THG) intensity. This material was thinned by a vacuum evaporation method. It was deposited on the glass substrate by vacuum evaporation to a volume of 500 liters. THG strength from TH from quartz glass
When the χ ⁽³⁾ value was obtained by comparing with the G intensity,
The fundamental wave was 1.5 μm and was about 7 × 10 ⁻¹¹ esu.

Example 2 TH in which 0.2 mol of 4-diethylaminocinnamaldehyde was dissolved in 0.1 mol of p-diacetylbenzene
An aqueous solution of 10% sodium hydroxide was added to 200 cc of the F solution, and the mixture was heated under reflux for one day. The precipitated crystals were recrystallized with a THF solution to obtain a compound B represented by the following formula (Formula 2), which is one of the materials of the present invention. (Melting point 260 ° C)

[0021]

[Chemical 2]

Next, the χ ⁽³⁾ value of the thin film of this material was measured by the third harmonic (THG) intensity. This material was thinned by a vacuum evaporation method. It was deposited on the glass substrate by vacuum evaporation to a volume of 500 liters. THG strength from TH from quartz glass
When the χ ⁽³⁾ value was obtained by comparing with the G intensity,
It was about 2 × 10 ⁻¹⁰ esu at a fundamental wave of 1.6 μm.

Example 3 0.2 mol of 1-diethylamino-4-acetylbenzene to 0.1 mol of 2,5-dichloroterephthalaldehyde
A 10% aqueous sodium hydroxide solution was added to 200 cc of a THF solution in which mols were dissolved, and the mixture was heated under reflux for 24 hours. The precipitated crystal was recrystallized with a THF solution to obtain a compound C represented by the following formula (Formula 3), which is one of the materials of the present invention.

[0024]

[Chemical 3]

Next, the χ ⁽³⁾ value of the thin film of this material was measured by the third harmonic (THG) intensity. This material was thinned by a vacuum evaporation method. It was deposited on the glass substrate by vacuum evaporation to a volume of 500 liters. THG strength from TH from quartz glass
When the χ ⁽³⁾ value was obtained by comparing with the G intensity,
The fundamental wave was 1.6 μm and was about 3 × 10 ⁻¹⁰ esu.

Example 4 A 10% aqueous sodium hydroxide solution was added to 200 cc of a THF solution in which 2 mol of 4- [ethyl (hydroxyethyl)] aminobenzaldehyde was dissolved in 1 mol of p-diacetylbenzene, and the mixture was heated under reflux for one day. .. The precipitated crystals were recrystallized with a THF solution to obtain a compound D represented by the following formula (Formula 4), which is one of the materials of the present invention.

[0027]

[Chemical 4]

Next, 1 mol of compound D was dissolved in THF and reacted with 1 mol of adipic dichloride at room temperature. The reaction product was reprecipitated with methanol to obtain one of the main chain polymer materials D'of the present invention in which the high χ ⁽³⁾ material of the present invention was incorporated into polyester.

The χ ⁽³⁾ value of a thin film of this material was measured by the third harmonic (THG) intensity. Thinning of this material was possible by spin coating. Χ with a 500 Å film
^{(3) When the} value was determined, a value of three-photon resonance χ ⁽³⁾ to 4 × 10 ^-11 esu was obtained at a fundamental wave of 1.5 μm. In addition, a film of about 4 μm can be easily formed from this material by spin coating, and a slab waveguide can be manufactured.
Excitation light source on wavelength side longer than absorption edge wavelength of film, wavelength 1.
When the waveguide loss was measured by the prism coupling method using a 3 μm LD laser, it was 1 dB / cm or less.

Next, 1 mol of the compound D was dissolved in THF and reacted with 1 mol of butylene diisocyanate at room temperature. The reaction product was reprecipitated with methanol to obtain D ″, which is one of the main chain polymer materials of the present invention material, in which the high χ ⁽³⁾ material of the present invention material was incorporated into polyurethane.

The χ ⁽³⁾ value of the spin coat film of this material was measured by the third harmonic (THG) intensity. When the χ ⁽³⁾ value was obtained for a 500 Å film, a value of three-photon resonance χ ⁽³⁾ to 4 × 10 ^-10 esu was obtained at a fundamental wave of 1.5 μm. Also, this material can be easily formed into a film of about 4 μm by spin coating, a slab waveguide can be produced, and the waveguide loss was measured using an excitation light source and an LD laser with a wavelength of 1.3 μm. It was 1 dB / cm or less.

Further, 1 mol of the compound D was dissolved in THF and reacted with 1 mol of methacrylic acid chloride at room temperature. The resulting methacrylic compound and methyl methacrylate were mixed at a molar ratio of 1: 2, enclosed with a polymerization initiator in a glass container, and allowed to react at 60 ° C. for 24 hours for copolymerization to obtain a polymer. The polymer was reprecipitated and purified with methanol to obtain a side chain type polymer material D ″ ″ of the present invention material.

The χ ⁽³⁾ value of the spin coat film of this material was measured by the third harmonic (THG) intensity. When the χ ⁽³⁾ value was obtained for a 500 Å film, a value of three-photon resonance χ ⁽³⁾ to 4 × 10 ^-11 esu was obtained at a fundamental wave of 1.5 μm. In addition, a film of about 10 μm can be easily formed from this material by spin coating, a slab waveguide can be manufactured, and the waveguide loss is measured using an excitation light source and an LD laser with a wavelength of 1.3 μm. It was 1 dB / cm or less.

Example 5 To a 200 ml solution of THF in which 2 mol of 4- [ethyl (hydroxyethyl)] aminocinnamaldehyde was dissolved in 1 mol of p-diacetylbenzene was added a 10% aqueous sodium hydroxide solution, and the mixture was heated under reflux for one day. did. The precipitated crystal was recrystallized with a THF solution to obtain a compound E represented by the following formula (Formula 5), which is one of the materials of the present invention.

[0035]

[Chemical 5]

Next, 1 mol of the compound E was dissolved in THF and reacted with 1 mol of adipic dichloride at room temperature. The reaction product was reprecipitated with methanol to obtain one of the main chain polymer materials E'of the present invention in which the high χ ⁽³⁾ material of the present invention was incorporated into polyester.

The χ ⁽³⁾ value of a thin film of this material was measured by the third harmonic (THG) intensity. Thinning of this material was possible by spin coating. Χ with a 500 Å film
^{When the} value ⁽³⁾ was determined, a value of three-photon resonance χ ⁽³⁾ to 8 × 10 ^-11 esu was obtained at a fundamental wave of 1.6 μm. Also, this material can be easily formed into a film of about 4 μm by spin coating, a slab waveguide can be produced, and the waveguide loss was measured using an excitation light source and an LD laser with a wavelength of 1.3 μm. It was about 1 dB / cm.

Then, 1 mol of the compound E was dissolved in THF and reacted with 1 mol of butylene diisocyanate at room temperature. The reactants were reprecipitated with methanol to obtain E ″, one of the main chain polymer materials of the material of the present invention, in which the high χ ⁽³⁾ material of the material of the present invention was incorporated into polyurethane. Membrane χ
^{(3) The} value is 500 Å, and it is ³ at the fundamental wave of 1.6 μm.
The photon resonance was χ ⁽³⁾ 〜 1 × 10 ^-10 esu. Also, this material can be easily formed into a film of about 4 μm by spin coating, a slab waveguide can be produced, and the waveguide loss was measured using an excitation light source and an LD laser with a wavelength of 1.3 μm. It was about 1 dB / cm.

Next, 1 mol of the compound E was dissolved in THF and reacted with 1 mol of methacrylic acid chloride at room temperature. The resulting methacrylic compound and methyl methacrylate were mixed at a molar ratio of 1: 2, enclosed with a polymerization initiator in a glass container, and allowed to react at 60 ° C. for 24 hours for copolymerization to obtain a polymer. The polymer was reprecipitated and purified with methanol to obtain a side chain type polymer material E ″ ″ of the material of the present invention. The χ ⁽³⁾ value of this material was determined to be ³ at a fundamental wave of 1.6 μm.
The values of photon resonance χ ⁽³⁾ -5 × 10 ^-11 esu were obtained. Also,
A film of about 10 μm can be easily formed from this material by spin coating, and a slab waveguide can be manufactured.
When the waveguide loss was measured using an excitation light source and an LD laser having a wavelength of 1.3 μm, it was 1 dB / cm or less.

Example 6 With respect to 1 mol of 2,5-dichloroterephthalaldehyde,
1 to 200 cc of THF solution containing 2 mol of 1- [ethyl (hydroxyethyl)] amino-4-acetylbenzene.
A 0% sodium hydroxide aqueous solution was added, and the mixture was heated under reflux for one day. The precipitated crystal was recrystallized with a THF solution to obtain a compound F represented by the following formula (Formula 6), which is one of the materials of the present invention.

[0041]

[Chemical 6]

Next, 1 mol of the compound F was dissolved in THF and reacted with 1 mol of hexylene diisocyanate at room temperature.
The reaction product was reprecipitated with methanol to obtain one of the main chain polymer materials of the present invention F'in which the high χ ⁽³⁾ material of the present invention was incorporated into polyurethane. The χ ⁽³⁾ value of the spin coat film of this material was measured by the third harmonic (THG) intensity.
When the χ ⁽³⁾ value was obtained for a 500 Å film, the fundamental wave was 1.6
The value of three-photon resonance χ ⁽³⁾ to 2 × 10 ^-10 esu was obtained at μm. This material can be easily spin-coated to form a film with a thickness of about 4 μm, and a slab waveguide can be produced. When the waveguide loss is measured using an excitation light source and an LD laser with a wavelength of 1.3 μm, it is 1 dB. It was about / cm.

Next, 1 mol of compound F was dissolved in THF and reacted with 1 mol of adipic dichloride at room temperature. The reaction product was reprecipitated with methanol to obtain F ″, which is one of the main chain type polymer materials of the present invention material, in which the high χ ⁽³⁾ material of the present invention material is incorporated in polyester. Membrane χ
^{(3) The} value was 500 Å thick, and was three-photon resonance χ ⁽³⁾ to 2 × 10 ^-10 esu at the fundamental wave of 1.6 µm. A slab waveguide can be easily produced by spin coating of this material, and the waveguide loss was measured to be about 1 dB / cm using an excitation light source and an LD laser having a wavelength of 1.3 μm.

Further, 1 mol of the compound F was dissolved in THF and reacted with 1 mol of methacrylic acid chloride at room temperature. The resulting methacrylic compound and methyl methacrylate were mixed at a molar ratio of 1: 2, enclosed with a polymerization initiator in a glass container, and allowed to react at 60 ° C. for 24 hours for copolymerization to obtain a polymer. The polymer was reprecipitated and purified with methanol to obtain a side chain type polymer material F ″ ″ of the present invention. The χ ⁽³⁾ value of this material was determined to be ³ at a fundamental wave of 1.6 μm.
The values of photon resonance χ ⁽³⁾ -10 ^-11 esu were obtained. This material was also capable of easily forming a film with a thickness of about 10 μm by spin coating, and was able to produce a slab waveguide. The waveguide loss was measured to be about 1 dB / cm.

Example 7 The high χ ⁽³⁾ materials GN of the present invention in another example are shown in Table 1.
And summarized in Table 2. The synthesis method of GN is described below.

[0046]

[Table 1]

[0047]

[Table 2]

A method of synthesizing G: 1 mol of 4-diethylamino-4'-nitrochalcone was added to T
It was dissolved in HF, 2 mol of zinc was dispersed, and the mixture was heated under reflux. The deposited precipitate was purified to obtain the compound G of the present invention.

Method of synthesizing H 4-diethylaminobenzaldehyde 1 mol and 4,4 '
-0.5 mol of diacetylstilbene was dissolved in THF, a small amount of aqueous NaOH solution was added, and the mixture was heated under reflux for 24 hours. The deposited precipitate was purified to obtain the compound H of the present invention.

◎ Synthesis Method of I Dissolve 1 mol of 4'-diethylamino-4-acetylchalcone and 0.5 mol of terephthalaldehyde in THF,
A small amount of NaOH aqueous solution was added, and the mixture was heated under reflux for 24 hours. The deposited precipitate was purified to obtain the compound I of the present invention.

⊚ Synthesis Method J 4-diethylaminocinnamaldehyde (1 mol) and 4-nitro-1-acetylbenzene (1 mol) were dissolved in THF, a small amount of an aqueous NaOH solution was added, and the mixture was heated under reflux for one day. The deposited precipitate was purified, dissolved in THF, 2 mol of zinc was dispersed, and the mixture was heated under reflux. The deposited precipitate was purified to obtain the compound J of the present invention.

Method of synthesizing K: 1 mol of 4'-diethylamino-4-acetylchalcone and 1 mol of 4-nitrobenzaldehyde were dissolved in THF, a small amount of an aqueous NaOH solution was added, and the mixture was heated under reflux for one day. The deposited precipitate was purified, dissolved in THF, 2 mol of zinc was dispersed, and the mixture was heated under reflux. The deposited precipitate was purified to obtain the compound K of the present invention.

⊚ Synthesis method of L 4-diethylaminocinnamaldehyde (1 mol) and p-diacetylbenzene (1 mol) were dissolved in THF, and NaOH was added.
A small amount of the aqueous solution was added, and the mixture was heated under reflux for one day. The precipitate that precipitates is purified, dissolved in THF, 0.9 mol of terephthalaldehyde is dissolved, and a small amount of NaOH aqueous solution is added,
The mixture was heated and refluxed for one day and night. The deposited precipitate was purified to obtain the compound L of the present invention.

Method of synthesizing M 1 mol of 4-diethylaminobenzaldehyde and 1 mol of acetone were dissolved in THF, a small amount of aqueous NaOH solution was added, and the mixture was heated under reflux for one day. The precipitate that precipitates is purified, and T
It was dissolved in HF, 0.9 mol of terephthalaldehyde was dissolved, a small amount of aqueous NaOH solution was added, and the mixture was heated under reflux for one day. The deposited precipitate was purified to obtain the compound M of the present invention.

◎ Synthetic Method of N 4-Acetylethenyl-1-diethylaminobenzene 1
Mol and 1 mol of terephthalaldehyde were dissolved in THF, a small amount of aqueous NaOH solution was added, and the mixture was heated under reflux for one day. The deposited precipitate is purified, dissolved in THF, and p-
0.9 mol of diacetylbenzene was dissolved, a small amount of NaOH aqueous solution was added, and the mixture was heated under reflux for one day. The deposited precipitate was purified to obtain the compound N of the present invention.

Regarding the polymer materials of the present invention in which the high χ ⁽³⁾ materials of G to N are used as basic skeletons, raw materials having OH groups at both ends are synthesized according to the above-mentioned synthesis examples of G to N,
The main chain type polymers (D ', E', shown in Examples 1 to 6)
F ′, D ″, E ″, F ″) or side chain type polymers (D ″ ″, E ″ ″, F ″ ″) can be synthesized in the same manner.

[0057]

As described above, the non-linear material of the present invention has high-speed and high-efficiency third-order non-linear optical characteristics, and is excellent in moldability and light transmission, so that it can be used in future optical computing and optical It can be widely used as a central material for optical nonlinear elements that play a role in switching technology. In terms of materials for optical gate optical switching devices, low χ ⁽³⁾ materials require lengthening and cannot be used unless the waveguide loss is extremely low. On the other hand, χ
^{Since the} material of ^{(3) has} a large optical path length, the requirement for waveguide loss is naturally low. Since the waveguide loss of this material is, for example, about 1 dB / cm, if the optical path length is 1 cm, χ
About 80% of ⁽³⁾ can be effectively used. If a waveguide having a cross-sectional area of 3 μm ^{2 and} a length of about 1 cm is produced, an optical gate optical switch device that can be sufficiently driven by a semiconductor laser can be realized. Regarding the device operating speed, it has already been confirmed that a CS ₂ solution exhibiting a molecular rotation effect can perform a switching operation of several picoseconds, and the material system without molecular rotation can operate in picoseconds or less. Further, it can be applied not only to the optical gate optical switching device but also to other important optical nonlinear devices such as an optical bistable device and an optical limiter device.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Toshikuni Kaino 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A third-order nonlinear optical material characterized in that both ends of the molecule are substituted with an alkylamino group and that it has two or more —CH═CH—CO— as a π-conjugated bond. 2. A third-order nonlinear optical material characterized in that the material according to claim 1 is incorporated in a main chain of a polymeric material.